I posted image about the arcane dmg to link above. 1 global, 3 casts, all same time into face, for 400k dmg on ~63% resil. None of em casted, all istants. Mage has crit reforges, (mastery=more dmg), no t2 wep etc.
This is what can be easily used in arena without tricks.
to do well over 500k dmg in just 3 casts needs timing and tricks, but possible, by actualy casting frost bomb, timing DF (noglobal) istant arcane blast->barrage. if u add one global there, fire blast, u dont have to even time DF with frost bomb.